Fatty acid separation



Jan. 11, 1949. c. c. 'rowNE FATTY ACID SEPARATION Filed July 17, 1945 INVENTOR 0mm 5J C lh/Ms'.

Patented' Je. n, i949 I UNITED STATES PATENTy [OFFICE o A m'rrxaizi'xnsssm'non charles cnrowue, Beacon, N. Y., assigner' n The Texas Company, vNew York, N. Y., a corpora.-

tion of Delaware Y' Application July v1'1, 194s, serial No. 605,610

This invention relatesto the fatty oil substances into their components by'a method which involves a combination of filtration and liquid phase extraction. y .I

Broadly. the invention contemplates leffecting fractional separation of a fatty. oil substance comprising solidifiable saturated constituents vand unsaturated constituents of differing degrees of unsaturation. The method involves precipitating saturated components of the feed mixture by dilution with an organic solvent liquid, and filtration of the precipitated material fromfthe mixture to form a filtrate comprising-unsaturated constituents of. the feed. This filtrate, either with or without removal of the solvent liquid, is subjected to liquid phase extraction with additional solvent liquid or with a different solvent liquid so as to form liquid extract and raffinate phases. The extract phase comprises the rela.

tively unsaturated constituents dissolved in the main body of solvent liquid, while the rafiinate phase comprises relatively less unsaturated ,constituents mixed with a portion of the solvent. The two phases are separately removed and the solvent liquid may be removed therefrom.

According to a modification of the invention,l

the liquid phase extraction may be carried out under conditions so as'to obtain a rough degree of separation between the desired components of the unsaturated fatty oil mixture. In such case, the resulting ranate phase, with or without the addition of more solvent liquid, is cooled or chilled to a temperature at which the less unsaturated component or components Aare pre4 cipitated. The resulting cold mixture is then subjected to filtration to separate the precipi-u tated constituents and produce a filtrate comprising the more unsaturated component or components dissolved in solvent liquid. This secon-V dary filtration is thus employed to obtain a more clear cut separation between components of the separation of -from a source not shown through a pipe 2. fatty acid feed and; acetone are mixed inthe s emma. (cieco-419i 'Ihe invention is effective for the fractional separation of fatty acid mixtures such as derlvedv from soy-bean oil, cottonseed oil, etc., and which mixtures consist essentially of palmitlc,

` stearic, oleic and linoleic acids.

A feature ofthe invention involvesl precipitating a saturated constituent such as stearic anc' palmitic acids from such a` fatty acid mixture to liquid phase extraction to effect separation between oleic and linoieic acids.

As already indicated, another feature of the invention involves utilizing the liquid phase extraction. step as an adjunct to a subsequent and secondary filtering operation for the purpose of obtaining a more clean cut separation between the fatty acids. Thus, the extraction step is used to reduce the concentration of the most unsaturatedconstituent or constituents in the mixture prior to the secondary filtration step.v

In this way the secondary filtration permits a clean cut separation of the residual unsaturated constituents into fractions of predetermined character, that'is with respect to the melting point range, iodine value, etc.

In order to describe the invention in more detail, reference will now be made to the accompanying drawing which comprises a iiow diagram illustrating the application of the invention to the treatment of a fatty acid mixture comprising about 50% linolenic acid, 30% oleic acid, 5% stearic acid, and about 8% palmitic acid, the mixture being characterized by having an iodine number of about 140.

Referring to the drawing. the fatty acid feed mixture is drawn from a source not shown through a pipe I- and mixed with a solvent liquid y' such as acetone or other low boiling ketone drawn The proportion off'about 2 to 3 volumes of acetone to l volume of fatty acid feed. The result-ing mixture is then' passed 'through a Chiller 3 wherein it is chilledto a temperature of about -59 F. or toa temperature in the range about 0 to -.10 F.

Advantageously the fatty acid mixturey may be mixed initially withabout 0.7 to 1.5 volumes of solvent liquid'per volume of fatty acid mixture, and this mixture chilled to the aforesaid temperature, following which the remainder of the The filter cake is subjected to washing with i additional solvent liquid in'situ as is customary in the conventional filter-practice. This wash solvent is advantageously chilled to about the iiltering temperature in a chiller 5 prior to introduction to the illter.

iiltrate and separately removed from the iilter through a dosage pipe 6 to which reference will be made later. The purpose of this washing is to remove mother liquor from the filter cake prior to discharge from the filter. The ilter cake is discharged from the filter through a pipe 1 and may be passed to a stripper a wherein retained solvent is stripped from the stearic and palmitic acids, the solvent free material'having an iodine number of not more than about 5.

The primary ltrate discharged from the filter 4 kand consisting of the unsaturated acids dissolved in solvent liquid is conducted through a pipe 9 to an extractor I0. The filtrate-may be passed rst to a stripper il wherein part or all of the solvent liquid is removed prior to passage to the extractor. This stripping is practiced when the same type of solvent is used in the subsequent extraction.

Also, the temperature of the filtrate or stripped ltrate may be adjusted by passage through the heat exchanger l2 prior to introduction to the extractor l0.

If the stripped iiltrate is extracted with acetone, it is introduced to the upper part ,of the extraction tower through a pipe i3. An addi-- tional quantity of acetone is conducted through a pipe I5 and a heater or heat exchanger I6 and introduced through a pipe l1 to the lower portion of the extractor l0.

When the solvent liquid used in the extractor l is of greater density than` the fatty acid mixture being charged thereto, such as nitrobenzene. furfural, aniline, phenol, etc., the points of introduction of fatty acid mixture and solventare reversed. nitrobenzene, is drawn from a source not shown through pipe |a, exchanger I8, pipe Il, and introduced through pipe Ila to the upper portion of extractor I0, while the nitrate, either without the aforesaid stripping, or with either partial or complete stripping of theV initial solvent, is passed through pipe |341 to the lower portion of the extractor.

The stream of acetone introduced to the lower portion of the extractor is caused to rise countercurrently to the descending body of filtrate so as to effect countercurrent extraction. Temperature conditions are maintainedv at about 70 to 150 F. within the extractor so that formation of l extract and raiiinate phases takes place.

The extract phase accumulating in the upper portion of the extractor comprises the most unsaturated constituent, namely linoleic acid dissolved in the major portion of the solvent liquid. This extract phase is drawn gli continuously Also, the wash filtrate is advantageously kept separate from the main i In such case, the solvent, such as 4 through a pipe I8 to a stripper i9 wherein the solvent is stripped from the acid.

'I'he solvent-free acid or substantially solventfree acid is drawn oi through a pipe 20 from which it may be' discharged from the system. Advantageousiy a portion of the solvent-free or substantially solvent-free acid is recycled to the `top of the tower through branch pipe 2l to providea back wash therein for the purpose oi displacing oleic acid from the phase mixture accumulating in the top of the tower. In this way .it is possible to draw oi an extract stream consisting essentially of linoleic acid dissolved in solvent liquid. After removal of the solvent, the linoleic acid is of about 99% purity.

The raiiinate phase collecting in the bottom of the extractor i0 comprises mainly oleic acid,

'and is drawn ofi through a pipe 22 and may be discharged from the system.

However, in accordance with the invention the ramnate phase stream is passed through a branch pipe 23 to a hea't exchanger 2l wherein it is cooled and from there passed through a cooler or chiller 25. Prior to introduction to the chiller 25, the ramnate phase is mixed with additional solvent liquid. When the same solvent is used in the extraction as in the primary iiltration, this additional solvent liquid advantageously comprises wash filtrate4 discharged from the primary illter through pipe 6 and to which reference has previouslybeen made. On the other hand. freshsolvent may be added through pipes 26 and 21.

. Conditions may be maintained in the extractor l0 so that the unsaturated acid contained in the ramnate phase passing through the pipe 22 will comprise about oleic acid and 5% linoleic acid..-.. The solvent present in the rafiinate phase mixture may amount to about 20% by volume. Accordingly, fresh solvent or wash filtrate ,is addedthrough the pipe 21 so as to provide a mixture. passing to the chiller .comprising about 3 .or 4 volumes of solvent to 1 `volume oi unsaturated acids.

This mixture is ,chilledfto a temperature of about -60 F., and the resulting chilled mixture passed to a illter, 30 wherein a filter cake is obe liquid. This nitrate is advantageously conduced through apipe 34 into the aforesaid heatv exchanger 24 wherein it is used to precool the aforesaid rafiinate phase mixture passing to the secondary illtration. The ltrate mixture after passage through exchanger 24 is conducted through pipe 35 to the upper portion of the extractor i'll and in this way recycled.

VWhile mention has been made of operating thel extractor i0 so as to-produce a raillnate mixture of unsaturated acids containing 95% oleic acid, nevertheless it is contemplated that the operation may b e conducted so as to produce amixture in which the linoleic acid may amount to 25 or 30%. From the standpoint of the sec-y .26 The filter Qlmy be operated in substrattien!l the same manner as the filter l'so thatthe filter cake is subjected to washing in situ with additional solvent liquid.

' Mention has been made of using acetone as a common solvent. However, itis contemplated that'a different solvent liquid may be used in the extraction and secondary filtration steps. Other solvent liquids besides acetone may be used such as methylethyl ketone, acetonitrile,

liquid sulfur dioxide, alcohols, and

Obviously many modifications and variations of the invention as above set forth may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

l. In the fractional separation of a higher fatty acid mixture comprising oleic and linoleic acids substantially freev from saturated acids, the method which comprises extracting said mixture with a low boiling aliphatic ketone in an extraction zone at a temperature in the range of about '70 to 150 F.,.forming as a result of said extraction, an extract phase rich'in linoleic acid, and a rainate phase in which linoleic acid ranges from about to 25% of the oleic acid present therein, and containing a relatively small proportion of solvent, separately removing saidacid, removing said filter cake and recycling re-l sulting filtrate to said extraction zone.

2. In the fractional separation of a higher fatty acid mixture comprising oleic and'linoleic acids substantially free from saturated acids, a method which comprises extracting said mixture with acetone in an extraction zone at a temperature in the range of about 70 to 150 F., forming as a result of said extraction an extract phase rich in linoleic acid and a ramnate phase in which linoleic acid ranges from about 5 to 25% of the oleic acid present therein andcontaining a relatively small proportion of solvent, separately removing said phases, adding an additional quantity of said solvent to remove raflinate phase thereby forming a mixture comprising about one volume of unsaturated fatty acid and about three to four volumes of solvent chilling resulting mixture of solvent and rainate phase to a temperature of about minus F. to precipitate oleic acid in substantially pure form, removing precipitated acid from the chilled liquid mixture of solvent and residual linoleic acid, and recycling, at least in part, said chilled mixture from which the precipitate has been removed to said extraction zone.

3. In the fractional separation of a fatty acid mixture comprising oleic and linoleic acids substantially free from saturated acids, the method which comprises passing va stream of said fatty acid mixture to the upper portion of an extraction tower, introducing a stream of low boiling ketone to the lower portion of said tower, causing fatty acid and solvent to flow countercurrently through said tower, maintaining said tower at a. temperature in the range of about '70 to 150 F.,

withdrawing from the top of said tower an extract phase rich in linoleic acid, withdrawing from the bottom of said tower a rafnate phase containing mainly oleic acid, and in which linoleic acid is-present in an amount ranging Vfrom about 5 to 25% of the oleic acid, separately removing said phases, adding an additional quantity of said solvent to withdrawn rainate phase thereby forming a mixture comprising about one volume of unsaturated fattyV acid and three to four volumes of solvent, chilling the resulting mixture to a temperature of .about 60 F., to precipitate oleic acid in substantially pure form, removing precipitated acid from the chilled liquid mixture of solvent and residual linoleic acid,

and recycling said chilled mixture from which the precipitate has been removed to the upper portion of said extraction tower. v

CHARLES o. ToWNE.

REFERENCES CITED The following references are of record in the ille of vthis patent:

UNITED STATES PATENTS Number Hartsuch, J. Am. Chem. Soc., vol. 61, May 1939, pp. 1142-44. 

